| 摘要 |
PURPOSE:To prevent the destruction of a power transistor in an inverter circuit by containing a PWM pattern, of which modulation rate changes for one period of a sine wave, in a control circuit so as to minimize a motor current change in the inverter circuit for outputting AC power to a motor. CONSTITUTION:In the built-in memory of a control circuit 15, PWM patterns for one period obtained by changing the ratio (modulation rate) of a sine wave to a triangular wave for one period of the sine wave are combined with PWM patterns for one period obtained without changing the modulation rate and there are also stored PWM patterns obtained in view of the relation between an inverter frequency and the output voltage of an inverter circuit 13. The inverter circuit 13 is controlled by a PWM control signal 16 outputted from the control circuit 15. As a result, the change of a motor current flowing through the inverter circuit 13 can be made small. Thus, there is a low possibility that an overcurrent flows through the inverter circuit 13, and it is consequently possible to prevent the destruction of a power transistor in the inverter circuit 13. |
